The present invention relates to a twin-clutch transmission system which comprises a first clutch for selecting a gear ratio in a first gear ratio group and a second clutch for selecting a gear ration in a second gear ratio group.
Japanese Patent Provisional Publication No. 8-320054 discloses a twin-clutch transmission which comprises two gear-ratio groups, for which clutches are provided, respectively. During when a gear ratio of one of the two gear ratio groups is selected, the clutch for the other gear ratio group is put in a neutral position.
In reply to a shift command generated by an operation of a shift lever, shifting is executed by the following manner:
1. The clutch for the gear-ratio group in a resting state is disengaged.
2. A desired gear ratio in the rest-state gear-ratio group is selected.
3. The clutch for an operating-state gear-ratio group is disengaged, and the clutch for the resting-state gear-ratio group is engaged. This is so-called changeover of the clutches.
4. A used gear-ratio of the operating-state gear-ratio group is put in a neutral position.
5. After recognizing that the used gear-ratio is put in the neutral position, the clutch for the resting-state gear-ratio group is engaged.
6. The desired gear ratio of the resting-state gear-ratio group is put in the engaged state.
However, this twin-clutch transmission is required to further quickly execute a shift operation.
It is therefore an object of the present invention to provide an improved twin-clutch transmission system which is capable of shortening a shift time by employing a pre-shift control.
An aspect of the present invention resides in a transmission system which comprises a twin-clutch transmission, an engine revolution speed detector detecting an engine revolution speed, a gear ratio detector detecting a present gear ratio selected from the gear ratios of the first and second gear-ratio groups, and a control unit. The twin-clutch transmission comprises a first shaft having gears for producing a first gear-ratio group, a second shaft having gears for producing a second gear-ratio group, a first clutch being capable of connecting the first shaft to an internal combustion engine so as to be selectable of one gear ratio of the first gear-ratio group, and a second clutch being capable of connecting the second shaft to the engine so as to be selectable of one gear ratio of the second gear-ratio group. The control unit coupled to the transmission, the engine revolution speed detector and the gear ratio detector. The control unit is configured to calculate an estimated engine revolution speed produced in the event that one of two gear ratios adjacent to the present gear ratio is selected by executing one of upshift and downshift, on the basis of the engine revolution speed, the present gear ratio and the one of the two gear ratios adjacent to the present gear ratio, to determine whether the estimated engine revolution speed is out of a normal engine revolution speed range, and to disengage one of the first and second clutches which is engaged to select the gear-ratio group including the other of the two gear ratios adjacent to the present gear ratio when the estimated engine revolution speed is out of the normal operation speed range.
Another aspect of the present invention resides in a transmission control system controlling a twin-clutch transmission which comprises a first clutch for connecting a first gear-ratio group to an internal combustion engine and a second clutch for connecting a second gear-ratio group to the engine, the transmission control system comprising: a control unit configured to obtain an engine revolution speed, to obtain a present gear ratio in operation, to calculate an estimated downshift engine revolution speed produced in the event that a downshift-side gear ratio adjacent to the present gear ratio is selected by downshift, on the basis of the engine revolution speed, the present gear ratio and the downshift-side gear ratio, to determine whether the estimated downshift engine revolution speed is out of a normal engine revolution speed range, to execute a pre-upshift control when the estimated downshift engine revolution speed is out of the normal engine revolution speed range, the pre-upshift control including an operation for disengaging the clutch for selecting the gear-ratio group which includes an upshift-side gear ratio adjacent to the present gear ratio, to calculate an estimated upshift engine revolution speed produced in the event that the upshift-side gear ratio is selected by upshift from the present gear ratio, on the basis of the engine revolution speed, the present gear ratio and the upshift-side gear ratio, to determine whether the estimated upshift engine revolution speed is out of a normal engine revolution speed range, and to execute a pre-downshift control when the estimated upshift engine revolution speed is out of the normal engine revolution speed range, the pre-downshift control including an operation for disengaging the clutch for selecting the gear-ratio group which includes the downshift-side gear ratio.
A further another aspect of the present invention resides in a method of controlling a twin-clutch transmission which comprises a first shaft having gears for producing a first gear-ratio group, a second shaft having gears for producing a second gear-ratio group, a first clutch being capable of connecting the first shaft to an internal combustion engine so as to be selectable of one gear ratio of the first gear-ratio group, and a second clutch being capable of connecting the second shaft to the engine so as to be selectable of one gear ratio of the second gear-ratio group, the method comprising: detecting an engine revolution speed; detecting a present gear ratio selected from the gear ratios of the first and second gear-ratio groups; calculating an estimated engine revolution speed produced when one of two gear ratios adjacent to the present gear ratio is selected by executing one of upshift and downshift, on the basis of the engine revolution speed, the present gear ratio and the one of the two gear ratios adjacent to the present gear ratio; determining whether the estimated engine revolution speed is out of a normal engine revolution speed range; and disengaging one of the first and second clutches which is engaged to select the gear-ratio group including the other of the two gear ratios adjacent to the present gear ratio when the estimated engine revolution speed is out of the normal operation speed range.